The present invention relates to a cast aluminum alloy product to which another member can be coupled by plastic deformation such as calking, a method of manufacturing thereof and also a coupling method using plastic deformation thereof.
A part, such as a protector in a braking system for an automobile enclosing a hydraulic circuit therein, has a regulator at an outlet of the hydraulic circuit for regulating a flow rate of oil. Since the regulator is generally made of steel or synthetic resin, which can not be fixed to the aluminum protector by welding, plastic deformation (e.g. calking) of the aluminum member has been adopted for fixing the regulator.
The aluminum protector for a braking system of an automobile is estimated to be plastically deformed for fixing other members, as mentioned above. In this regard, such a wrought alloy as Al—Si—Mg relatively high of toughness has been used so far for such the purpose. However, since the wrought alloy is relatively expensive compared with a cast alloy, it is expected to provide a protector made of a cheap cast alloy.
A cast aluminum alloy product generally includes such cast defects as blowholes and comprises a metallurgical structure wherein α-Al phase comes out as a matrix with ununiform grain size. Segregation of an eutectic Si phase grown to a coarse size as well as dispersion of primary Si are often observed in the matrix. Due to such the metallurgical structure, the cast aluminum alloy product is poor of ductility and so regarded as a member improper to be coupled with another member by plastic deformation.
In actual, JP 6-145866A discloses a cast aluminum alloy product for use as a protector of an automobile braking system, whereby growth of isometric crystals is promoted by addition of Ti and B to reduce occurrence of blowholes. Even the proposed aluminum alloy product is insufficient of ductility, so it can not be yet used as a member to be coupled with another member.